Projection device

ABSTRACT

A projection device includes an optical lens and a light source. The optical lens has an incident surface of light, a reflecting surface that has a concave curved surface and internally reflects light that has entered through the incident surface, and an exit surface of light that has been reflected by the reflecting surface. The light source that emits light that enters the optical lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2020-151706 filed on Sep. 10, 2020, theentire contents of which are incorporated herein by reference.

BACKGROUND Technical Field

The technical field relates to a projection device.

Description of Related Art

Conventionally, there is a light source device that adjusts direction oflight rays emitted by a light source in an appropriate direction andoutputs it with high directionality. In a device that outputs desiredcolor images, such as a projector, light of multiple wavelength bands iscombined and output. JP 2016-57375 A discloses a projector that diffusesa part of light emitted by a laser light source of a blue wavelengthband, converts the rest of the light into light of a green wavelengthband using phosphors, and then combines them again for output.

SUMMARY

According to an aspect of the present disclosure, there is provided aprojection device including:

an optical lens that has an incident surface of light, a reflectingsurface that has a concave curved surface and internally reflects lightthat has entered through the incident surface, and an exit surface oflight that has been reflected by the reflecting surface; and

a light source that emits light that enters the optical lens.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments, and together with thegeneral description given above and the detailed description of theembodiments given below, serve to explain the principles of the presentdisclosure, wherein:

FIG. 1 is a diagram illustrating configurations of a projector and lightemission paths;

FIG. 2A is a diagram illustrating an irregular-shaped lens;

FIG. 2B is a diagram illustrating the irregular-shaped lens;

FIG. 2C is a diagram illustrating the irregular-shaped lens;

FIG. 3A is a diagram illustrating a light path in the irregular-shapedlens; and

FIG. 3B is a diagram illustrating a light path in the irregular-shapedlens.

DETAILED DESCRIPTION

In the followings, an embodiment of a projection device will bedescribed.

FIG. 1 is a diagram of the projection device of this embodiment,explaining configurations of a projector 1 including a light sourcedevice and the light output path.

The projector 1, which is a projection device, includes a laser diode(LD11; light source) and a light-emitting diode (LED17) as lightsources, and emits light of RGB colors using these light sources. TheLD11 emits light of a blue wavelength band. Here, for example, fourTO-CAN type LDs 11 are aligned and emit parallel rays of light. An LED17 emits light of a red wavelength band. The light of a green wavelengthband is obtained by a phosphor based on the light of the blue wavelengthband, as described later. In FIG. 1 , the light path of the bluewavelength band is shown with solid arrows, the light path of the greenwavelength band is shown with dashed-dotted arrows, and the light pathof the red wavelength band is shown with dashed arrows.

Various optical devices are located on the optical paths. The opticaldevices here include a reflective mirror group 21, a collimating lens22, collimating lens groups 23, 25, 28, 29, dichroic filters 24, 30, anirregular-shaped lens 26, a reflective mirror 27, and the like. On thelight path of the blue wavelength band, a fluorescent wheel 40 islocated.

After the light of the three wavelength bands has been combined (merged)by the dichroic filter 30, the light is emitted through the merged lightguide 50, a display element 60, and a projection lens group 70. Themerged light guide 50 reflects the merged parallel rays of light ofrespective wavelength bands in an appropriate direction and guides it tothe display element 60.

The display element 60 is a spatial optical modulator (SOM), forexample, a digital micromirror device (DMD). The DMD switches tiltangles of respective micromirrors arranged in an array at high speed oneby one, determines whether or not light is reflected toward theprojection lens group 70 for each pixel unit or each image frame unit,and forms an optical image with the reflected light.

The projection lens group 70 guides and emits the optical image emittedby the display element 60 in the output direction. The projection lensgroup 70 includes a plurality of lenses whose combination or positionalrelationship can be changed such that its focal position, themagnification (zoom) of the output image, and the like can be adjusted.

The fluorescent wheel 40 is a circular metal plate that has an area witha phosphor layer and a diffusion transmission surface. When the phosphorlayer is irradiated with light of the blue wavelength band, light of thegreen wavelength band is excited and emitted. The diffusion transmissionsurface transmits the light of the blue wavelength band while diffusingit. The fluorescent wheel 40 is rotatably driven by a motor 41. As aresult, the fluorescent wheel 40 emits light of the green wavelengthband (of a different wavelength) based on a part of the light of theblue wavelength band, and causes light other than the part to enter thediffusion transmission surface as it is.

The diffused and transmitted light of the blue wavelength band entersthe irregular-shaped lens 26, passes through the reflective mirror 27,the collimating lens 28, and then the dichroic filter (second dichroicfilter) 30 (first light guide), and is guided to the merged light guide50. The light of the green wavelength band emitted from the phosphorlayer returns to the collimating lens group 25, is reflected by thedichroic filter 24 (first dichroic filter), passes through thecollimating lens 29, is then reflected by the dichroic filter 30 (secondlight guide), and is guided to the merged light guide 50.

The light of the red wavelength band that is emitted by the LED 17 andis less diffused because of the collimating lens group 23, passesthrough the dichroic filter 24, is then reflected by the dichroic filter30, and is guided to the merged light guide 50.

In other words, the dichroic filter 24 transmits the light of the blueand red wavelength bands and selectively reflects the light of the greenwavelength band. The dichroic filter 30 selectively transmits the lightof the blue wavelength band and reflects the light of the green and redwavelength bands.

The light source device of this embodiment includes, among theabove-described configurations, those along the respective paths oflight of the blue wavelength band and the light of the green wavelengthband from LD 11 where light of the blue wavelength band is emitted, tothe dichroic filter 30 where light of the blue and green wavelengthbands are combined, in particular, the fluorescent wheel 40, the motor41, and the irregular-shaped lens 26.

Next, the irregular-shaped lens 26, which is an optical lens of thisembodiment, will be explained.

FIG. 2A to FIG. 2B show the irregular-shaped lens 26. As shown in FIG.2A, the irregular-shaped lens 26 is different from other lenses in thatits optical axis on a side of an incident surface P1 (incident opticalaxis X1) is oriented differently from its optical axis on a side of anexit surface P3 (outgoing optical axis X3). Here, the incident opticalaxis X1 (here, along the Z direction) and the outgoing optical axis X3(here, along the X direction) are perpendicular to each other. Theirregular-shaped lens 26 has a reflecting surface P2 at whichorientation of the optical axis changes inside the irregular-shaped lens26.

As shown in FIG. 2B, FIG. 2C, etc., the incident surface P1 has a convexportion B (protrusion) that protrudes from a flat surface. The convexportion B has a spherical surface (three-dimensional shape of aspherical cap) and functions as a convex lens that collimates theincident light. Here, the convex portion B has a shape (curvature) thatat least reduces diffusion of the light that has been transmitted whilebeing diffused through the diffusion transmission surface of thefluorescent wheel 40. The position and size of the convex portion B aredetermined such that almost all the light of the blue wavelength bandfrom the diffusion transmission surface of the fluorescent wheel 40enters the convex portion B.

The incident light entering the irregular-shaped lens 26 through theincident surface P1 is reflected by the reflecting surface P2 in theirregular-shaped lens 26. The reflecting surface P2 has a concave curvedsurface (convex shape when viewed from the outside) having a shapeformed by extending a quadratic curve perpendicular to a plane on whichthe quadratic curve is present. Here, the reflecting surface P2 has ashape of a portion of a cylinder surface (quadratically curved surface).The cross section of the curved surface cut by a plane parallel to theincident optical axis X1 and the outgoing optical axis X3 (XZ plane orfirst plane) has a shape of a quadratic curve having a focus on thediffusion transmission surface of the fluorescent wheel 40, for example,a parabola shape. The reflection surface P2 extends in a straight linein the direction perpendicular to both the incident optical axis X1 andthe outgoing optical axis X3 (Y-axis direction, normal to the firstsurface). The irregular-shaped lens 26 is made of optical glass whoserefractive index is approximately 1.5. The reflecting surface P2 isoriented depending on the material so that most of the incident light istotally reflected. However, because not all the incident light isreflected depending on the direction of the incident light, theirregular-shaped lens 26 may have a reflective layer R on the outer sideof the reflecting surface P2. Depending on an incident angle on theincident surface P1, positional relationship between the incidentsurface P1 and the reflecting surface P2, and the refractive index, thearea in the reflecting surface P2 where total reflection may not occuris limited.

Therefore, the reflective layer R does not need to cover the entireouter surface of the reflecting surface P2, but only needs to beprovided in such a way that reflection occurs with a small loss in thearea where total reflection does not occur. Because of the reflectingsurface P2 shaped as described above, the incident light is collimated(diffusion is suppressed) in the XZ plane (first plane) in the directionof the outgoing optical axis X3.

The convex portion B is sized and located such that the incident lighton the incident surface P1 can efficiently strike the appropriate areaof the reflecting surface P2. Here, the convex portion B is located atthe center of the incident surface P1 in the Y direction, and is shiftedfrom the center toward the −X side in the X direction. Accordingly, theconvex portion B may have a shape of a trimmed spherical cap, that is, aspherical cap from which a part protruding from the incident surface P1is removed. The removed part specifically corresponds to a part of thespherical cap on the −X side of an YZ plane. The YZ plane isperpendicular to the bottom of the spherical cap shape and includes the−X side edge of the incident surface P1.

The exit surface P3 is straight in the Z direction (the direction normalto the second plane) and has a shape of a portion of a cylinder whosecross-section parallel to the XY plane (a second plane that is parallelto the normal of the first plane) has a shape of a quadratic curve(here, a circular arc shape). As a result, the incident light is notcollimated by the reflecting surface P2 when viewed in the XY plane butis collimated so as to be in parallel with the outgoing optical axis X3by the exit surface P3, thereby the outgoing light is parallel rays oflight. Here, the incident optical axis X1 is perpendicular to theoutgoing optical axis X3.

The incident surface P1 and the exit surface P3 may have ananti-reflection layer. The anti-reflection layer may be a well-knowncoating layer.

FIG. 3A and FIG. 3B are diagrams illustrating light paths in theirregular-shaped lens 26. FIG. 3A illustrates the light path in the XZplane, and FIG. 3B illustrates the light path in the XY plane.

As shown in FIG. 3A, in the XZ plane, the light of the blue wavelengthband from the fluorescent wheel 40 is collimated so as to be almostparallel rays of light, and is output from the exit surface P3 becauseof the convex surface of the convex portion B and the concave surface ofthe reflecting surface P2. As shown in FIG. 3B, in the XY plane,diffusion of the light of the blue wavelength band from the fluorescentwheel 40 is not reduced by reflection at the reflecting surface P2, butis reduced at the exit surface P3. Thus, the irregular-shaped lens 26 ofthis embodiment uses a combination of the reflecting surface P2 and exitsurface P3 to emit collimated light.

As described above, the irregular-shaped lens 26, the optical lens ofthis embodiment, has the incident surface P1 where light enters, thereflecting surface P2 that internally reflects the light having enteredfrom the incident surface P1, and the exit surface P3 of the lighthaving been reflected by the reflecting surface P2. The reflectingsurface P2 has a shape of a concave curved surface.

The conventional optical system including combination of a collimatinglens and a mirror to output light in an appropriate direction has beenfacing a problem of difficulty in downsizing the system because thesystem requires a space to bend the light while suppressing diffusion ofthe light.

The irregular-shaped lens 26 in the above embodiment enables collimationand change in the optical axis direction due to reflection collectivelyand in a compact manner. In particular, since a convex portion of aconventional convex lens for collimation occupies a large space, it isnecessary to leave a large space between such convex lens and otherconfigurations such as mirrors. Therefore, according to theirregular-shaped lens 26 of this application, the components of theoptical system can be arranged with less limitations. Furthermore,almost total reflection of the incident light inside theirregular-shaped lens 26 can cause less losses than the reflection usinga conventional mirror. Therefore, the irregular-shaped lens 26 canchange the direction of light while efficiently collimating light(reducing light diffusion).

The reflecting surface P2 has a quadratically curved surface. As aresult, the irregular-shaped lens 26 having a simple shape canefficiently collimate the incident light and convert it into parallelrays of light.

The reflecting surface P2 has a shape of a portion of a cylinder(parabolic curved cylinder) surface that extends linearly in a directionof a normal to the first plane (Y direction). The cross-section of thecylinder surface has a quadratically curved (for example, parabolic)shape when cut by a plane parallel to the first plane (XZ plane). Theexit surface P3 has a shape of a portion of a cylinder (circularcylinder) surface that extends linearly in a direction of a normal tothe second plane (Z direction). The cross-section of the cylindersurface has a quadratically curved shape (circular arc) when cut by aplane parallel to the second plane (XY plane) parallel to a normal tothe first plane.

Since the reflecting surface P2 and the exit surface P3 individuallyperform collimation of light in this manner, they each can be formed ina two dimensionally curved shape. Therefore, it is easy to manufacturethe irregular-shaped lens and to efficiently set the path of the light.

The exit surface P3 has a shape of a portion of a cylinder surface. Thisallows the irregular-shaped lens 26 to convert the diffused incidentlight into parallel rays of light easily and in a short distance.

The irregular-shaped lens 26 emits parallel rays of light from the exitsurface P3. In this way, the irregular-shaped lens 26 not only reflectsand bends the light as a prism does, but also reduces diffusion of lightand emits the light. Because a mirror and a collimating lens do not needto be arranged separately, it is possible to set the light path in amore space-saving manner.

The outgoing optical axis X3 of the light emitted from the exit surfaceP3 is perpendicular to the incident optical axis X1 of the incidentlight on the incident surface P1. That is, this irregular-shaped lens 26can perform bending of the light path in 90 degrees and the lightcollimation (suppressing light diffusion to forma parallel rays oflight) simultaneously in a space-saving manner.

The irregular-shaped lens 26 has the reflective layer R at least at apart of the outer side of the reflecting surface P2 to reflect lightthat is not reflected by the reflecting surface P2. The irregular-shapedlens 26 may not fully reflect the light depending on the angle ofincidence, because the reflecting surface P2 is not flat, the phosphorlayer is quite close to the incident surface P1, and so on. In suchcases, the reflective layer R is preferably provided in a required area.With such a configuration, losses can be reduced as compared toreflection using a mirror only, and light can be reflected andcollimated in a compact manner.

Furthermore, the incident surface P1 has the convex portion B of aspherical surface shape. This allows the irregular-shaped lens 26 toreduce diffusion degree of the diffused incident light to a certainextent. As a result, the reflecting surface P2 and the exit surface P3can be shaped more freely.

The convex portion B has a shape of a trimmed spherical cap. If aspherical cap that is located corresponding to an incident area thatefficiently allows light to reach the reflecting surface P2 protrudesfrom the incident surface P1, the convex portion B of the incidentsurface P1 may have a shape of the spherical cap from which thisprotruding portion is removed. This does not cause any opticalinconvenience and allows the irregular-shaped lens 26 to have a compactshape without an extra protruding portion.

The light source device included in the projector 1 (projection device)of this embodiment includes the above-mentioned irregular-shaped lens 26and the LD 11 that emits light that enters the irregular-shaped lens 26.In other words, this light source device can be compact and output lightemitted by the LD11 in an appropriate direction.

The light source device also includes fluorescent wheel 40 having thephosphor layer that emits, based on a part of the light of the bluewavelength band emitted by the LD 11, light of the different wavelengthband (green), and the diffusion transmission surface that transmits thelight of the blue wavelength band while diffusing it. Light transmittedby the diffusion transmission surface enters the irregular-shaped lens26. The quadratically curved cylinder surface of the reflecting surfaceP2 has its focus on the diffusion transmission surface (assuming a crosssection of the reflecting surface P2 cut by the XZ plane in thedrawing). In other words, by compactly setting a path for a part of thelight to be emitted, the size of the entire light source device can bereduced.

The light source device also includes the first light guide that guidesthe light emitted through the irregular-shaped lens 26, the second lightguide that guides the light emitted by the phosphor layer, and themerged light guide 50 where the light through the first light guide andthe light through the second light guide are merged and guided. That is,when light of a certain wavelength and light of another wavelength passthrough different paths to be merged, one of the paths, in particularthe longer path, can be compactly set using the irregular-shaped lens 26so that the size of the light source device can be reduced.

The present invention is not limited to the above embodiment, andvarious changes can be made.

For example, the reflecting surface P2 and the exit surface P3 haverespective quadratically curved cylinder surface shapes so as to makethe light rays parallel to respective planes that are orthogonal to eachother in the above embodiment, but the present invention is not limitedthereto. The reflecting surface P2 may have a quadratically curvedsurface such as a paraboloid to orient the light rays parallel to astraight line at a time. In this case, the exit surface P3 may be just aflat surface. Alternatively, reflecting surface P2 and the exit surfaceP3 each may be such a quadratically curved surface that collimates lightstep by step. The reflecting surface P2 and the exit surface P3 are notlimited to the quadratically curved surfaces, but may be, for example,third-order or higher-order surfaces such that fine aberrations arereduced, and the like.

In the above-described embodiment, parallel rays of light are emitted asan example, but the present invention is not limited thereto, as long asdiffusion of the emitted light is suppressed compared to that of theincident light. Alternatively, the light may be emitted in a moreconverged manner.

In the above-described embodiment, the irregular-shaped lens 26 bendsthe optical axis at a right angle and has the exit surface P3 and theincident surface P1 perpendicular to each other, but the presentinvention is not limited thereto. The irregular-shaped lens can beconfigured to bend the optical axis of the outgoing light byappropriately 90 degrees taking manufacturing errors into account, orany other angle.

In the above-described embodiment, the irregular-shaped lens 26 has thereflecting layer R, but does not have to have the reflecting layer R ifnot necessary, considering the relationship between the incident angleof the incident light, the reflection angle at the reflecting surfaceP2, and the material (refractive index) of the irregular-shaped lens 26.

In the above-described embodiment, the incident surface P1 has a convexportion B having a spherical surface shape to suppress light diffusion,but the present invention is not limited thereto. When the incidentlight is not diffused so much, the incident surface P1 may not have theconvex portion B. The incident surface of the convex portion B may haveany other quadratically curved surface shape. The convex portion B maynot have a partially removed spherical cap shape, depending on theposition and size of the spherical cap shape that constitutes the convexportion B.

In the above-described embodiment, the light emitted by the LD 11 entersthe irregular-shaped lens 26, but the present invention is not limitedthereto. Any other light source may be used.

In the above-described embodiment, light of the green wavelength band isemitted by the phosphor layer, but the present invention is not limitedthereto. There may be a further light source that emits light of thegreen wavelength band. Alternatively, light of the green wavelength bandmay be generated not by the phosphor layer but by a filter or the like.

In the above-described embodiment, light of the blue wavelength bandenters the irregular-shaped lens 26, but light of other wavelength bandsmay enter the irregular-shaped lens 26. Also, the incident light is notlimited to light of a single wavelength band. In this case, the incidentangle of the light may be different for each wavelength band.

In the above-described embodiment, the light source device emits lightof multiple wavelength bands, but may emit light of only a singlewavelength band. Furthermore, the light is not limited to visible lightas long as it is light of a wavelength band that can pass through a lensand can be reflected by a mirror. For example, infrared light may beincluded. Also, light of multiple wavelength bands does not necessarilyhave to be merged and output.

In the above-described embodiment, the light source device is one forthe projector 1, but the present invention is not limited thereto. Thelight source device may be used in various applications such as lightingdevices, signs, inspection devices, and the like.

In addition, the specific configuration, contents and procedures ofprocessing, and the like described in the above embodiment can bechanged as necessary without departing from the gist of the presentinvention.

Although several embodiments of the present invention have beendescribed above, the scope of the present invention is not limited tothe embodiments described above, but includes the scope of the presentinvention described in the claims and the scope of their equivalents.

What is claimed is:
 1. A projection device comprises: an optical lensthat has an incident surface of light, a reflecting surface that has aconcave curved surface and internally reflects light that has enteredthrough the incident surface, and an exit surface of light that has beenreflected by the reflecting surface; and a light source that emits lightthat enters the optical lens; and a fluorescent wheel that has aphosphor layer and a diffusion transmission surface, the phosphor layerexciting light of a green wavelength band in response to irradiationwith light of a blue wavelength band, and the diffusion transmissionsurface transmitting light of the blue wavelength band, wherein light ofthe blue wavelength band that has been emitted by the light source andtransmitted by the diffusion transmission surface enters the incidentsurface.
 2. The projection device according to claim 1, wherein theincident surface has a protrusion having a spherical surface shape. 3.The projection device according to claim 2, wherein light that entersthe protrusion is reflected by the reflecting surface having aquadratically curved surface shape, and is then emitted through the exitsurface.
 4. The projection device according to claim 3, wherein theprotrusion has a shape of a trimmed spherical cap.
 5. The projectiondevice according to claim 3, wherein the exit surface has a shape of aportion of a cylinder that enables parallel rays of light to be emittedthrough the exit surface.
 6. The projection device according to claim 3,wherein an outgoing optical axis of light through the exit surface issubstantially perpendicular to an incident optical axis of light throughthe incident surface.
 7. The projection device according to claim 3,further comprising: a reflective layer that is provided on at least apart of an outer side of the reflecting surface and reflects light thatis not reflected by the reflecting surface.
 8. The projection deviceaccording to claim 2, wherein the protrusion has a shape of a trimmedspherical cap.
 9. The projection device according to claim 8, whereinthe exit surface has a shape of a portion of a cylinder that enablesparallel rays of light to be emitted through the exit surface.
 10. Theprojection device according to claim 8, wherein an outgoing optical axisof light through the exit surface is substantially perpendicular to anincident optical axis of light through the incident surface.
 11. Theprojection device according to claim 8, further comprising: a reflectivelayer that is provided on at least a part of an outer side of thereflecting surface and reflects light that is not reflected by thereflecting surface.
 12. The projection device according to claim 2,wherein the exit surface has a shape of a portion of a cylinder thatenables parallel rays of light to be emitted through the exit surface.13. The projection device according to claim 2, wherein an outgoingoptical axis of light through the exit surface is substantiallyperpendicular to an incident optical axis of light through the incidentsurface.
 14. The projection device according to claim 2, furthercomprising: a reflective layer that is provided on at least a part of anouter side of the reflecting surface and reflects light that is notreflected by the reflecting surface.
 15. The projection device accordingto claim 1, wherein the exit surface has a shape of a portion of acylinder that enables parallel rays of light to be emitted through theexit surface.
 16. The projection device according to claim 15, whereinan outgoing optical axis of light through the exit surface issubstantially perpendicular to an incident optical axis of light throughthe incident surface.
 17. The projection device according to claim 1,wherein an outgoing optical axis of light through the exit surface issubstantially perpendicular to an incident optical axis of light throughthe incident surface.
 18. The projection device according to claim 1,further comprising: a reflective layer that is provided on at least apart of an outer side of the reflecting surface and reflects light thatis not reflected by the reflecting surface.
 19. The projection deviceaccording to claim 1, further comprising: a first dichroic filter thattransmits light of a blue wavelength band and a red wavelength band andreflects light of a green wavelength band; and a second dichroic filterthat transmits light of a blue wavelength band and reflects light of agreen wavelength band and a red wavelength band.
 20. A projection devicecomprising: an optical lens that has an incident surface of light, areflecting surface that has a concave curved surface and internallyreflects light that has entered through the incident surface, and anexit surface of light that has been reflected by the reflecting surface;a light source that emits light that enters the optical lens; and areflective layer that is provided on at least a part of an outer side ofthe reflecting surface and reflects light that is not reflected by thereflecting surface.
 21. An optical lens comprising: an incident surfaceof light; a reflecting surface that has a concave curved surface andinternally reflects light that has entered through the incident surface;an exit surface of light that has been reflected by the reflectingsurface; and a reflective layer that is provided on at least a part ofan outer side of the reflecting surface and reflects light that is notreflected by the reflecting surface.